Imaging device

ABSTRACT

A lens control device, for controlling driving of a second lens unit for correcting image movement regarding movement of a variating first lens unit, comprises: a storage unit for storing data indicating the position of the second lens unit corresponding to the position of the first lens unit created for a predetermined focal distance; a control unit for generating information to control driving of the second lens unit based on the data, and for controlling driving of the second lens unit based on this information; and a distance detecting unit for detecting distance to the focus object; wherein the control unit restricts the range of the generated information based on the detection results from the distance detecting unit. Or, the control unit controls driving for the second lens unit to generate the information, and performs weighting based on detection results from the distance detecting unit relating to driving control.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/965,472filed Oct. 13, 2004 now U.S. Pat. No. 7,415,200, which claims priorityfrom Japanese Patent Application Nos. 2003-354372 filed Oct. 14, 2003,and 2003-361291 filed Oct. 21, 2003, all of which are herebyincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to optical equipment such as a videocamera, digital camera, and so forth.

2. Description of the Related Art

With regard to cameras with non-interchangeable lenses, there aredemands for reduction in size, the ability to photograph subjects fromas close as possible, and so forth. Therefore, rather than interlockinga correcting lens and a variable power lens mechanically by a cam, aso-called inner focus type lens is becoming mainstream, wherein themovement locus of the correcting lens is input in advance as lens camdata within a microcomputer, which drives the correcting lens accordingto this lens cam data, and further sets the focus by means of thiscorrecting lens.

FIG. 8 is a figure that illustrates the configuration of a lens systemwith the current inner focus type. Here, reference numeral 901 denotes afixed front lens, 902 denotes a zoom lens for variable power (alsoreferred to as a variator lens: first lens unit), 903 denotes anaperture diaphragm, 904 denotes a fixed lens that is fixed, and 905denotes a focus lens (second lens unit) to be used as a correcting lens,which provides a focal point adjusting function and a function thatcorrects the movement of the image based on the variable power. Further,906 denotes an imaging plane.

With a lens system configured as in FIG. 8, the focus lens 905 providesboth a compensator function and a focal point adjusting function,therefore even if the focal point distance is equal, the position of thefocus lens 905 for converging with the imaging plane 906 differs basedon the subject distance. When the subject distance is changed withregard to each focal point distance, and when the position of the focuslens 905 is continuously plotted to focus with the subject image on theimaging plane 906, the result is as shown in FIG. 9. While zooming in orout, selecting a locus corresponding to the subject distance from themultiple loci illustrated in FIG. 9 moves the focus lens 905 accordingto the selected locus, thereby enabling variable power (zooming) whilestoring the focused state.

Now, with regards to the type of a lens system where the front lensperforms the focusing, a focus lens independent of the zoom lens isprovided, and further, the zoom lens and the focus lens are mechanicallylinked to a cam ring. Therefore, in the case of trying to rotate the camring manually and change the focal point for example, even if the camring is moved very fast, the cam ring follows and rotates. The zoom lensand the focus lens move in the direction of the optical axis, accordingto the cam formed by the cam ring, and therefore, is the focus lens isin a converging position, the image will not blur due to zooming.

In contrast to this, a lens system of an inner focus type generallyrecords in memory the information of the multiple loci illustrated inFIG. 9 (also called electronic cam locus) or the informationcorresponding to this (in other words, either information indicating thelocus itself, or a function wherein the lens position is a variable, issuitable), selects a locus based on the positions of the focus lens andthe zoom lens, and performs zooming while moving along the selectedlocus.

Now, in the case that the zoom lens moves in the direction fromtelephoto to wide angle, focus can be maintained using theabove-described locus following method, because it converges from astate wherein multiple loci have a given amount of spacing in between,as is apparent from FIG. 9. However, in the direction from wide angle totelephoto, the focus lens that was at the convergence point is uncertainwhich locus to follow, and therefore focus cannot be maintained with asimilar locus following method.

Therefore, Japanese Patent No. 2,795,439 (Claims, FIGS. 3 and 4, and thedescription thereof) discloses a control method (zigzag movement)wherein, using an AF evaluation value signal (sharpness signal) obtainedfrom the high frequency component of the image signal by using a TV-AFmethod, when moving the zoom lens (variable power), the focus lens isforced to move so as to be off focus from the focus position, andfurther, performs repeated control of switching and moving the focuslens toward the direction of focus (changing the following speed to thelocus), thereby correcting the following locus. Further, Japanese PatentNo. 2,795,439 discloses a method of changing the increase/decrease cycleof the sharpness signal by means of changing the amount of change of thefollowing speed corresponding to the subject, the focal point distance,and the depth of field, and attempts improvement of selection(generating) accuracy of the following locus selection.

The zigzag movement disclosed in the aforementioned Japanese Patent No.2,795,439 specifies the following locus based on the change of the AFevaluation value. Further, the evaluation value changes not onlyaccording to the status of blurring of the image, but also changesaccording to the pattern changes of the subject. Therefore, consideringthat there may be cases wherein the focus lens movement switching isswitched in the wrong direction, the correction range of the followinglocus is set as a wide range so as to be able to return to the correctlocus even if initially moving in the wrong direction.

On the other hand, when the setting is for such a wide correction range,in the event that the movement deviates from the locus that should beused, the image may blur until moved back to the correct locus. Further,in the case of moving the focus lens in the wrong direction, imageblurring may occur wherein the AF evaluation value level in particularis greatly decreased, or when image-taking a subject with low contrast,the correct locus may not be found, and there is the possibility thatthe image blur is carried all the way to the telephoto edge.

Further, in the case of image-taking a subject with a high frequency,when the following locus is trying to be set by means of the zigzagmovement, arbitrary image blurring can occur. In order to make this typeof image blurring less conspicuous, the AF evaluation value level, whichdetermines the reverse timing of the drive direction of the focus lenswherein the zigzag movement can be adjusted according to the subjectconditions, can be adjusted, but eliminating the occurrence of all imageblurring of the subject related to the zigzag movement is difficult.

Further, with the TV-AF method, due to the signal detection cycleobtained by the AF evaluation value being a vertical synchronizingsignal cycle, the sharpness of locus selection becomes poorer as thezooming speed becomes faster, and consequently, the rate of mistakenfollowing locus selection increases.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a lens controldevice, optical equipment, and a lens control method for performing highquality zooming that is not affected by the photography scene or camerawork, while maintaining a state of focus, even with a high speed zoom.

To this end, according to one aspect of the present invention, a lenscontrol device, for controlling the driving of a second lens unit forcorrecting image movement in the event of movement of a variating firstlens unit, comprises: a storage unit for storing data indicating theposition of the second lens unit corresponding to the position of thefirst lens unit created for a predetermined focal distance; a controlunit for generating information to control the driving of the secondlens unit based on the data, and for controlling the driving of thesecond lens unit based on this information; and a distance detectingunit for detecting the distance to the focus object; wherein the controlunit restricts the range of the generated information based on thedetection results from the distance detecting unit.

According to another aspect of the present invention, a lens controlmethod, for controlling the driving of a second lens unit for correctingimage movement in the event of movement of a variating first lens unit,comprises: a storage step for storing data indicating the position ofthe second lens unit corresponding to the position of the first lensunit created for a predetermined focal distance; a control step forgenerating information to control the driving of the second lens unitbased on the data, and for controlling the driving of the second lensunit based on this information; and a distance detecting step fordetecting the distance to the focus object; wherein, in the controlstep, the range of the generated information is restricts based on thedetection results from the distance detecting unit.

Here, the information may be locus information for showing the positionof the second lens unit as relates to the first lens unit or a parameterfor identifying this locus, or may be position information for drivingthe second lens unit.

According to another aspect of the present invention, a lens controldevice, for controlling the driving of a second lens unit for correctingimage movement in the event of movement of a variating first lens unit,comprises: a storage unit for storing data indicating the position ofthe second lens unit corresponding to the position of the first lensunit created for a predetermined focal distance; a control unit forgenerating information to control the driving of the second lens unitbased on the data, and for controlling the driving of the second lensunit based on this information; and a distance detecting unit fordetecting the distance to the focus object; wherein the control unitcontrols the driving for the second lens unit to generate theinformation, and performs weighting based on the detection results fromthe distance detecting unit relating to the drive control.

According to another aspect of the present invention, a lens controlmethod, for controlling the driving of a second lens unit for correctingimage movement in the event of movement of a variating first lens unit,comprises: a storage step for storing data indicating the position ofthe second lens unit corresponding to the position of the first lensunit created for a predetermined focal distance; a control step forgenerating information to control the driving of the second lens unitbased on the data, and for controlling the driving of the second lensunit based on this information; and a distance detecting step fordetecting the distance to the focus object; wherein in the control step,the driving of the second lens unit for generating the information iscontrolled, and weighting is performed based on the detected distance,relating to the driving control.

Here, weighting may be weighting relating to the drive direction ordrive speed of the second lens unit, or relating to the conditions forswitching the driving conditions in the case of driving theaforementioned second lens unit while switching the driving conditions.

Further, the information may be locus information for indicating theposition of the second lens unit as relates to the first lens unit or aparameter for identifying this locus, or may be a position informationfor driving the second lens unit.

Further objects, features and advantages of the imaging device, thefocus control method, and the processing program, according to thepresent invention, will become apparent from the following descriptionof the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the configuration of a video cameraaccording to first, second, and third embodiments.

FIG. 2 is a conceptual diagram illustrating the correction range of thecorrection movement of the cam locus according to the first, second, andthird embodiments.

FIGS. 3A and 3B are flowcharts illustrating the actions of a videocamera according to the first embodiment.

FIGS. 4A and 4B are flowcharts illustrating the underlying art of thepresent invention.

FIG. 5 is a flowchart illustrating the underlying art of the presentinvention.

FIG. 6 is a flowchart illustrating the underlying art of the presentinvention.

FIG. 7 is a flowchart illustrating the underlying art of the presentinvention.

FIG. 8 is a conceptual diagram illustrating the configuration of aconventional photography optical system.

FIG. 9 is a conceptual diagram illustrating the focus locuscorresponding to the conventional subject distance.

FIG. 10 is a diagram describing the focus locus.

FIG. 11 is a diagram describing the interpolation of the movementdirection of the zoom lens.

FIG. 12 is a diagram describing an example of a data table of the focuslocus.

FIGS. 13A and 13B are both conceptual diagrams illustrating theunderlying art of the present invention.

FIG. 14 is a conceptual diagram illustrating the underlying art of thepresent invention.

FIG. 15 is a diagram for describing triangulation.

FIG. 16 is a diagram for describing a distance measurement methodaccording to phase-difference detection.

FIG. 17 is a flowchart illustrating the actions of a video cameraaccording to the third embodiment.

FIG. 18 is a flowchart illustrating the actions of a video cameraaccording to the third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be describedbelow with reference to the drawings.

(Underlying Art)

Prior to describing the embodiments of the present invention, thetechnology that is the premise to the present invention will bedescribed.

FIG. 10 is a diagram for describing one example of the locus followingmethod for a focus lens in an inner focus type lens system.

In FIG. 10, Z₀, Z₁, Z₂, . . . Z₆ indicate the position of the zoom lens,and a₀, a₁, a₂, . . . a₆ and a₀, b₁, b₂, . . . b₆ indicate the positionof the focus lens corresponding to the subject distance stored in anunshown microcomputer beforehand. The group of these focus lenspositions (a₀, a₁, a₂, . . . a₆ and a₀, b₁, b₂, . . . b₆) becomes thefocus loci that the focus lens of the representative subject distancesshould follow (representative locus).

Further, p₀, p₁, p₂, . . . p₆ are the locations on the focus locus thatthe focus lens should follow, calculated based on the aforementioned tworepresentative loci. The Equation for the positions on this focus locuswill be illustrated below.P _((n+1)) =|p _((n)) −a _((n)) |/|b _((n))−(a)|×|b _((n+1)) −a _((n+1))|+a _((n+1))  (1)

According to the above Equation (1), for example in the case of FIG. 10wherein the focus lens is at p0, the ratio wherein p0 internally dividesthe line segment b₀-a₀ is calculated, and the point that internallydivides line segment b₁-a₁ according to this ratio is taken as p₁. Fromthe difference in location of this p₁-p₀ and from the time required forthe zoom lens to move from Z₀ to Z₁, the movement speed of the focuslens in order to maintain focus is determined.

Next, a case in which the stopping position of the zoom lens is notrestricted to the boundary of the zoom area that has the storedrepresentative locus data will be described. FIG. 11 is a diagram fordescribing the interpolation method of the zoom lens movement direction,wherein one portion of FIG. 10 is extracted and the position of the zoomlens is arbitrary.

In FIG. 11, the vertical axis illustrates the focus lens position, andthe horizontal axis illustrates the zoom lens position. When the zoomlens position is Z₀, Z₁, . . . Z_(k−1), Z_(k), . . . Z_(n), the focuslens position on the representative locus stored in the microcomputeris, according to the subject distance,a₀, a₁, . . . a_(k−1), a_(k), . . . a_(n)b₀, b₁, . . . b_(k−1), b_(k), . . . b_(n)

Now, in the case wherein the zoom lens position is at Z_(x) which is noton the zoom area boundary, and the focus lens position is P_(x), thena_(x) and b_(x) are calculated as follows:a _(x) =a _(k)−(Z _(k) −Z _(x))×(a _(k) −a _(k−1))/(Z _(k) −Z_(k−1))  (2)b _(x) =b _(k)−(Z _(k) −Z _(x))×(b _(k) −b _(k−1))/(Z _(k) −Z_(k−1))  (3)

In other words, following the current zoom lens position and the twozoom area boundary positions that are on either side (for example, Z_(k)and Z_(k−1) in FIG. 11) thereof and the division ratio obtainedtherefrom, a_(x) and b_(x) can be calculated by dividing those with thesame subject distance of the stored four representative locus data(a_(k), a_(k−1), b_(k), b_(k−1) in FIG. 11) using the above-describeddivision ratio.

Next, following the division ratio obtained from a_(x), p_(x), andb_(x), p_(k) and p_(k−1) can be calculated by dividing that of thepreviously stored aforementioned four representative data with identicalfocal distance, by the above-described division ratio as in Equation(1).

Then, when zooming from wide angle to telephoto, the movement speed ofthe focus lens in order to maintain focus is determined from thedifference in focus position p_(k) where the following movement isheaded, and the current focus position p_(x), and from the time requiredfor the zoom lens to move from Z_(x) to Z_(k).

Further, when zooming from telephoto to wide angle, the movement speedof the focus lens in order to maintain focus is determined from thedifference in focus position p_(k−1) where the following movement isheaded, and the current focus position p_(x), and from the time requiredfor the zoom lens to move from Z_(x) to Z_(k−1).

FIG. 12 illustrates an example of the table data of the focus locusinformation stored in the microcomputer beforehand. FIG. 12 illustratesthe focus lens position data A_((n, v)) based on subject distance, whichchanges according to the zoom lens position. The subject distancechanges with according to a variable n in the row direction, and thezoom lens position (focal distance) changes according to a variable v inthe column direction. Here, n=0 denotes an infinitely distant subjectdistance, and as n grows larger, the subject distance changes towardsthe greatest close-up distance side. n=m indicates a subject distance of1 cm. On the other hand, v=0 denotes the wide-angle end. Further, as vgrows larger and the focal distance increases, v=s denotes the zoom lensposition on the telephoto end. Therefore, one row of table data plotsone representative locus.

Next, as described above, a locus following method will be described forsolving the problem wherein the focus lens cannot find which locus tofollow when zooming from the wide angle to the telephoto direction.

In FIGS. 13A and 13B, the horizontal axis illustrates the position ofthe variable power lens. Further, the vertical axis in FIG. 13Aillustrates the AF evaluation signal obtained from the imaging signal bymeans of the TV-AF Equation. This AF evaluation signal illustrates thelevel of the high frequency components of the imaging signal (thesharpness signal). Further, the horizontal axis in FIG. 13B illustratesthe focus lens position. In FIG. 13B, reference numeral 1304 denotes thecam locus (grouping of the focus lens positions) that the focus lensshould travel when zooming while obtaining focus of the subject at agiven distance position.

Here, the standard movement speed for focus locus following when furtherat the wide angle side than the zoom lens position 1306 (Z₁₄) is made tobe positive (moving in the direction of focus lens close-up), and thestandard movement speed for focus locus following when moving in theinfinitely distant direction when further at the telephoto side than theposition 1306 is made to be negative. As the focus lens moves over thetarget locus 1304 while maintaining focus, the strength of the AFevaluation signal becomes the level denoted by 1301 in FIG. 13A.Generally, with zooming wherein focus is maintained, the AF evaluationsignal is approximately a set value.

In FIG. 13B, the standard movement speed of the focus lens that tracesthe target locus 1304 while zooming is V_(f0). The actual focus lensmovement speed is V_(f), and in the event of zooming while increasingand decreasing this movement speed V_(f) compared to the standardmovement speed V_(f0), the locus thereof becomes a zigzag locus as in1305 (hereafter, this is called “zigzag correction operation”).

At this time, the AF evaluation signal level changes so as to producemountains and valleys as indicated by 1303 in FIG. 13A. Here, at theposition wherein the target locus 1304 and the actual zigzag locus 1305intersects, the AF evaluation signal level 1303 becomes the greatestlevel 1301 (the even-numbered points of Z₀, Z₁, Z₂, . . . Z₁₆), and atthe odd-numbered points of Z₀, Z₁, Z₂, . . . Z₁₆ wherein the movementdirection vector of the actual locus 1305 switches, the AF evaluationsignal level 1303 becomes the smallest level 1302.

Then, conversely, if the value TH1 of the smallest level 1302 of the AFevaluation signal level 1303 is set in advance (in other words, thefocus tolerance is set wherein the AF evaluation signal of the smallestlevel TH1 that can be considered to be focused is the lower limit), andif the movement direction vector of the locus 1305 is switched each timethe AF evaluation signal level 1303 becomes the same size as TH1, thefocus lens movement direction after switching can be set in thedirection closer to the target locus 1304. In other words, whenever theimage is blurred by the difference of the greatest level 1301 and thesmallest level 1302 (TH1) of the AF evaluation signal, zooming can beperformed while controlling the occurrence of blurring by controllingthe drive direction and drive speed which are drive conditions for thefocus lens to reduce this blurring.

By using this type of method, as illustrated in FIG. 9, with zoomingfrom wide angle to telephoto wherein the focus loci of different subjectdistances spread out from convergence, even if the standard movementspeed V_(f0) that maintains focus is not the most appropriate for thesubject distance at that time, the movement speed V_(f) can becontrolled against the standard movement speed (calculated usingp_((n+1)) obtained from Equation (1)), and by repeating the switchingoperation indicated in locus 1305 according to the changes of the AFevaluation signal level, focus locus re-identifying (re-generating) canbe performed without the AF evaluation signal level moving below thesmallest level 1302 (TH1), in other words, without producing any morethan a predetermined amount of blurring. Further, by setting TH1appropriately, zooming is realized wherein the blurring is imperceptibleto the naked eye.

Here, with the focus lens movement speed V_(f) compared to the standardmovement speed set at V_(f+), for the positive direction correctionspeed, and at V_(f−) for the negative direction correction speed,V _(f) =V _(f0) +V _(f+)  (4)orV _(f) =V _(f0) +V _(f−)  (5)hold. At this time, the correction speeds V_(f+) and V_(f−) aredetermined by the direction vector of V_(f0) so as to equally divide theinterior angle of the two V_(f) direction vectors obtained by Equations(4) and (5), so as not to produce any imbalanced selection of thefollowing locus according to the aforementioned zooming method.

The zooming control described above generally performs processingsynchronizing to the image vertical synchronizing signal, from therelationship wherein the focus detection is performed using the imagingsignal from the imaging device.

FIG. 7 is a flowchart of the zooming control performed within themicrocomputer. Upon processing beginning in step S701, initial settingsare made in S702. At the time of initialization, the RAM within themicrocomputer and each port is initialized.

In S703, the state of the camera main unit operating system is detected.The microcomputer receives the information of the zoom switch unit forthe photographer to operate here, and displays the variable poweroperation information such as the zoom lens position on the display toadvise the photographer that it is in the process of zooming. In S704,AF processing is performed. In other words, automatic focus adjustmentprocessing is performed corresponding to the changes in the AFevaluation signal.

In S705, zooming processing is performed. In other words, the processingis performed for the compensator operation for maintaining the focuswhile zooming. Specifically, calculations are performed for the focuslens standard drive direction and standard drive speed, in order totrace the locus illustrated in FIG. 10 closely.

S706 is a routine that selects which to use of the drive direction ordrive speed of the zoom lens or focus lens, that were calculated in theS704 to S705 processing routine, in the case of AF or zooming, anddrives the zoom lens and focus lens between the telephoto edge and wideangle edge, or between the close-up edge and the infinity edge, undercontrol provided by software so as not to hit the mechanical edge.

In S707, a control signal is output to the motor driver, correspondingto the drive direction information and drive speed information forzooming and focusing determined in S706, and controls the drive/stop ofthe lens. After completing processing in S707, the flow returns to S703.The series of processes illustrated in FIG. 7 is performed synchronouslywith the vertical synchronizing signal (stands by in the processing ofS703 until the next vertical synchronizing signal is input).

FIGS. 3A through 4B illustrate the control flow executed within themicrocomputer once every vertical synchronizing signal, and illustratein detail the content of the processing executed in S705 of FIG. 7. Now,In FIGS. 3A through 4B, the portions indicated by the same circlednumeral are connected to one another.

The descriptions below will make reference to FIG. 5 through FIG. 7, andFIG. 10.

In S400 in FIG. 5, the drive speed Zsp of the zoom motor is set so as toperform natural zooming operations, corresponding to the operationinformation of the zoom switch unit.

In S401, the distance from the current position of the zoom lens andfocus lens to the subject (subject distance) is identified (estimated),and that subject distance information is stored memory region such asRAM, as three locus parameters (data for obtaining the target positioninformation) α, β, and γ. Here, the processing illustrated in FIG. 5 isperformed. Now, in order to simplify the description, the processingillustrated in FIG. 5 will be described as if the focus state ismaintained at the current lens position.

In S501 of FIG. 5, with the wide angle edge to the telephoto edge in thedata table illustrated in FIG. 12 divided into s equal segments, atwhich zoom area v the current zoom lens position Z_(x) is currentlylocated, is calculated.

In S601, the zoom area variable v is cleared. In S602, the zoom lensposition Z_((v)) on the boundary of the zoom area v is calculated,according to the following Equation (6). This Z_((v)) is equal to thezoom lens position Z₀, Z₁, Z₂, . . . illustrated in FIG. 10.Z _((v))=(telephoto edge zoom lens position−wide angle edge zoom lensposition)×v/s+wide angle zoom lens position  (6)

In S603, whether the Z_((v)) obtained in S602 is equal to the currentzoom lens position Z_(x) is determined. If equal, in S607, 1 is raisedas the boundary flag, as the zoom lens position Z_(x) is positioned onthe boundary of the zoom area v.

If not equal in S603, in S604 whether Z_(x)<Z_((v)) is determined. IfYes in S604, then Z_(x) is between Z_((v−1)) and Z_((v)), and theboundary flag in S606 is 0. If No in S604, then in S605 the zoom area vis incremented and the flow returns to S602.

By repeating the above process, whether or not the current zoom lensposition Z_(x) exists in the v=k′th zoom area on the data table in FIG.12, and whether or not Z_(x) is on the zoom area boundary, can be toldat the time of completing the flow shown in FIG. 6.

Returning to FIG. 5, the current zoom area is set in S501 by the processin FIG. 6, and according the following process calculates where on thedata table in FIG. 12 the focus lens is positioned.

First, in S502 the subject distance variable n is cleared, and in S503whether the current zoom lens position exists on the boundary of thezoom area is determined. If the boundary flag is 0, it is assumed not tobe on the boundary, and the flow continues to the process starting atS505.

In S505, Z_((v)) is set for Z_(k), and further Z_((v−1)) for Z_(k−1).Next, in S506, the four table data sets A_((n, v−1)), A_((n, v)),A_((n+1, v−)), A_((n+1, v)) are read out, and in S507 a_(x) and b_(x)are calculated from the above-described Equations (2) and (3).

On the other hand, in the event that S503 determines the boundary flagto be 1, in S504 the focus position A_((n, v)) corresponding to the zoomlens position (v in this case) of the subject distance n, andA_((n+1, v)) corresponding to the zoom lens position of the subjectdistance n+1, are called up and each stored in memory as a_(x) andb_(x), respectively.

In S508 whether the current focus lens position p_(x) is greater thana_(x) is determined. If greater than a_(x), in S509 whether or not thecurrent focus lens position p_(x) is greater than b_(x) is determined.If not greater than b_(x), the focus lens position p_(x) is determinedto be between the subject distances n and n+1, and the locus parametersat this point are recorded in memory from S513 to S515. At S513,α=p_(x)−a_(x), at S514, β=b_(x)−a_(x), and at S515, γ=n.

S508 is negative in the case that the focus lens position p_(x) is atthe far infinite distance position. At this time, in S512 α=0 is set andcontinued from the process of S514, and the locus parameter for infinitedistance is stored in memory.

S509 is positive in the case that the focus lens position p_(x) is atthe far close-up position, and in this case, in S510 the subjectdistance n is incremented, and in S511 whether n is on the side ofinfinite distance from the position m corresponding to the far close-updistance is determined. If to the side of infinite distance from the farclose-up distance position m, the flow returns to S503. S511 is negativein the case that the focus lens position p_(x) is at the far close-upposition, and the locus parameters for the far close-up distance arestored in memory by continuing from the process starting at S512 at thistime.

Returning to FIG. 4A, in S401, the locus parameters is stored in memoryin order to know which position on the locus illustrated in FIG. 9 thecurrent zoom lens position and the focus lens position are located.

In S402, the zoom lens position Z_(x)′ (the target position from thecurrent position) wherein the zoom lens will arrive after one verticalsynchronizing period (1V), is calculated. Here, if the zoom speeddetermined in S400 is Zsp (pps), the zoom lens position Z_(x)′ after onevertical synchronizing period can be found from the Equation (7) below.A pps is an increment of the rotation speed of the stepping motor, anddenotes the step amount (1 step=1 pulse) of rotation during 1 second.Further, the symbols in Equation (7) represent the movement direction ofthe zoom lens, + meaning the telephoto direction and − meaning the wideangle direction.Z _(x) ′=Z _(x) ±Zsp/vertical synchronizing frequency  (7)

Next, S403 determines which zoom area v′ wherein Z_(x)′ exists. In S403,the same process as the process in FIG. 6 is performed, and Z_(x) inFIG. 6 is substituted with Z_(x)′, and v with v′.

Next, in S404, whether the zoom lens position Z_(x)′ after one verticalsynchronizing period exists on the zoom area boundary is determined, andif the boundary flag=0, the zoom lens position Z_(x)′ is not consideredto be on the boundary, and the flow continues from the process startingin S405.

In S405, Z_(k)←Z_((v′)), and Z_(k−1)←Z_((v′−1)) are set. Next, in S406,the four table data sets A_((γ, v′−1)), A_((γ, v′)), A_((γ+1, v′−1)),A_((γ+1, v′)) wherein the subject distance γ is specified by the processin FIG. 5, and calculates a_(x)′ and b_(x)′ from the Equations (2) and(3) described above in S407. On the other hand, in the case that S403yields Yes, in S408 the focus position A_((γ, v′)) corresponding to thezoom area v′ of the subject distance γ, and the focus positionA_((γ+1, v′)) corresponding to the zoom area v′ of the subject distanceγ+1 are called up, and stored in memory as a_(x)′ and b_(x)′,respectively.

Then in S409, the focus lens focus position (target position) p_(x)′when the zoom lens position has reached Z_(x)′ is calculated. UsingEquation (1), the following target position after one verticalsynchronizing period can be expressed as follows.P _(x)′=(b _(x) ′−a _(x)′)×α/β+a _(x)′  (8)

Therefore, the difference ΔF of the following target position and thecurrent focus lens position becomesΔF=(b _(x) ′−a _(x)′)×α/+a _(x) ′−P _(x)

Next, in S410 the focus standard moving speed V_(f0) is calculated.V_(f0) is obtained by subtracting the focus lens position difference ΔFfrom the movement time of the zoom lens required to move this distance.

The calculation method for the correcting speed for performing the focuslens movement speed correction (zigzag operation) illustrated in FIG.13B will be described below.

In S411, each parameter is initialized, and the “reversal flag” used inthe later processes is cleared. S412 calculates the correction speedV_(f+) and V_(f−) for the “zigzag correction operation” from the focusstandard movement speed V_(f0) obtained in S410.

Here, the correction amount parameter δ and the correction speedsV_(f+), V_(f−) are calculated as follows. FIG. 14, which is a diagram todescribe the calculation method of the correction speeds V_(f+) andV_(f−) corresponding to the correction amount parameter δ, illustratesthe zoom lens position on the horizontal axis, and the focus lensposition on the vertical axis. 1304 is the target locus to be followed.

Now, the focus speed at which the focus lens position changes by anamount of y when the zoom lens position changes by an amount of x, (inother words, arrives at the target position), is the standard speedV_(f0) calculated in 1403. The focus speed at which the focus lensposition changes by an amount of n or m, with displacement y as areference, when the zoom lens position changes by an amount of x, is thecorrection speed V_(f+) and V_(f−) to be calculated. Here, n and m aredetermined so that the direction vector 1401 of the speed to drivecloser to the close-up side than the displacement y (the speed whereinthe correction speed V_(f+) is added to the standard speed V_(f0) in thepositive direction), and the direction vector 1402 of the speed to drivecloser to the infinite distance side than the displacement y (the speedwherein the correction speed V_(f−) is added to the standard speedV_(f0) in the negative direction), have direction vectors separatedequal angles δ as to the direction vector 1403 of the standard speedV_(f0).

First, m and n are obtained. From FIG. 14 in diagram form,tan θ=y/x, tan(θ·δ)=(y·m)/x, tan(θ+δ)=(y+n)/x  (9)Further,tan(θ±δ)=(tan θ±tan δ)/{1±(−1)×tan θ×tan δ}  (10)Further, from Equations (9) and (10),m=(x2+y2)/(x/k+y)  (11)n=(x2+y2)/(x/k·y)  (12)

wherein tan δ=k

whereby n and m can be calculated.

Here the correction angle δ is a variable for parameters such as thedepth of the subject field depth or focal distances. By using this, theincrease/decrease cycle of the AF evaluation signal level that changescorresponding to the focus lens drive state can be kept constant as tothe assigned focus lens position change amount, and the possibility ofmissing the focus locus that the focus lens should be following duringthe zooming can be reduced.

Within the memory of the microcomputer according to the value of δ, thevalue of k is stored as the data table, and by reading out as necessary,the Equations (11) and (12) are calculated.

Here, in the case that the zoom lens position changes by an amount of xeach time unit,Zoom speed Zsp=x,Focus standard speed V_(f0)=y, andCorrection speed V_(f+)=n, V_(f−)=mhold, and the correction speeds V_(f+) and V_(f−) (negative speed) areobtained by Equations (11) and (12).

In S413, whether or not zooming is being performed is determined,according to the information illustrating the operational state of thezoom switch unit obtained in S703 of FIG. 7. In the event that zoomingis being performed, the process starting at S416 is carried out. In theevent that zooming is not being performed, a value TH1 is set, wherein aarbitrary constant μ is subtracted from the current value of the AFevaluation signal level at S414. This TH1 determines the AF evaluationsignal level that is the switchover base point for the correctiondirection vector (switchover base point for the zigzag correctionoperation), as described in FIG. 13A. This TH1 is to be determinedimmediately prior to the start of zooming, and corresponds to thesmallest level of 1302 in FIG. 13A.

Next, in S415 the correction flags are cleared, and this process ends.Here, the correction flag is a flag indicating whether the locusfollowing state is under correction in the positive direction(correction flag=1) or under correction in the negative direction(correction flag=0).

In the event that S413 determines that zooming is being performed,determination is made whether or not the zooming direction is from wideangle to telephoto in S414. If from telephoto to wide angle, in S419V_(f+)=0 and V_(f−)=0 is set, and the processing starting from S420 isperformed. If from wide angle to telephoto, in S417 whether or not thecurrent AF evaluation signal level is smaller than TH1 is determined. IfTH1 or greater, the flow continues to S420, and if smaller than TH1, inS418 the reversal flag is set to 1 to perform correction directionswitching since the current AF evaluation signal level has dropped tobelow the TH1 (1302) level in FIG. 13.

In S420, whether the reversal flag is 1 is determined, and in the eventthat the reversal flag=1, then in S421 whether the correction flag is 1is determined. If the correction flag is not 1 in S421, then in S424 thecorrection flag is set to 1 (correction state in the positivedirection). Further, according to Equation (4),focus lens movement speed V _(f) =V _(f0) +V _(f+)

(wherein V_(f+)≧0).

On the other hand, if the correction flag=1 in S421, then in S423 thecorrection flag is set to 0 (correction state in the negativedirection), and according to Equation (5),focus lens movement speed V _(f) =V _(f0) +V _(f−)

(wherein V_(f−)≦0).

Further, in the event that the reversal flag is not 1 in S420, S422determines whether the correction flag=1. If the correction flag=1 theflow continues to S424, and if not, the flow continues to S423.

After completing this process, in S706 in FIG. 7 the focus lens and zoomlens drive direction and drive speed are selected, according to theoperation mode. In the case of zooming operation, the focus lens drivedirection is set to the close-up direction or the infinite distancedirection, depending on whether the focus lens movement speed V_(f)obtained in S423 or S424 is positive or negative. Thus, the locus to betraced is re-identified as the focus lens zigzag driving is performed.

The above-described is the underlying conventional art upon which thepresent invention has been made, and the description below will be madeprimarily contrasting the embodiments of the present invention with theconventional art.

First Embodiment

FIG. 1 shows an embodiment according to the present invention of animaging device (optical device) provided with a lens control device, asthe configuration of a video camera. Now, the present embodimentdescribes an example applying the present invention to a imaging devicewith non-interchangeable image-taking lens, however the presentinvention can also be applied to an interchangeable lens (opticalequipment) of an imaging system possessing an interchangeable lens andthe camera main unit to which this is attached. In this case, amicrocomputer within the lens performs the later-described zoomingoperation in response to a signal that is sent from the side of thecamera main unit. Further, the present invention is not limited to avideo camera, and may be used for a digital camera or various imagingdevices.

In FIG. 1, in order from the object side, reference numeral 101 denotesa fixed front lens unit 101, 102 denotes a zoom lens unit (first lensunit) that performs variation by moving along the optical axis, 103denotes an aperture diaphragm, 104 is a fixed lens unit that is fixed,105 denotes a focus lens unit (second lens unit), which provides a focusadjusting function and a compensator function that corrects the imagemovement from the variator, moving along the optical axis. Theimage-taking optical system configured of these lens units is a rearfocus optical system configured of four lens units possessing theoptical power of positive, negative, positive, positive in order fromthe object side (left side of diagram). Now, the diagram is drawnshowing one lens making up each lens unit, but in actuality, each lensunit may be made up of either a single or multiple lenses.

Reference numeral 106 is a imaging device, such as a CCD or a CMOSsensor. The light flux from an object that passes through theimage-taking optical system forms an image on the imaging device 106.The imaging device 106 takes the formed object image and performsphotoelectric conversion, and outputs image-taking signals. Theimage-taking signals are amplified to the optimum level with anamplifier (AGC) 107 and input into the camera signal processing circuit108. The camera signal processing circuit 108 outputs the input imagingsignal to the amplifier 110 after the input imaging signal is convertedto a standard television signal. The television signal that is amplifiedto the optimum level by the amplifier 110 is output to a magneticrecording/playing device 111, and is recorded on a magnetic recordingmedium such as a magnetic tape. Or, other different recording media maybe used, such as semiconductor memory or an optical disk.

Further, the television signal amplified by the amplifier 110 is alsosent to a LCD display circuit 114, and is displayed on a LCD 115 as ataken image. Now, the LCD 115 also displays images such as thephotography mode, image-taking conditions, warnings, etc., to becommunicated to the user. Such images are superimposed on the takenimage and displayed, by means of a camera microcomputer 116 controllinga character generator 113, and mixing the output thereof with televisionsignals on the LCD display circuit 114.

On the other hand, the imaging signals input to the camera signalprocessing circuit 108 can be simultaneously compressed with internalmemory and stored on a still image recording medium 112 such as a cardmedium.

Further, the imaging signal input into the camera signal processingcircuit 108 is also input into an AF signal processing circuit 109 as afocus information production means. The AF evaluation value signal(focus signal) that is formed in the AF signal processing circuit 109 isread out as data through transmission with a camera microcomputer 116.

Further, the camera microcomputer 116 reads in the zoom switch 130 andAF switch 131 states, and further detects the state of the photo switch134.

In the state wherein the photo switch 134 is pressed halfway, the focusoperation by the AF begins, and locks the focus when at a focused state.Further, in the fully pressed (deep press) state, this locks the focusregardless of whether in focus or out of focus, reads images into thememory (not shown) within the camera signal processing circuit 108, andperforms still image recording to the magnetic tape or still imagerecording medium 112.

Now, the camera microcomputer 116 determines whether to use amoving-image image-taking mode or a still-image image-taking mode,according to the state of the mode switch 133, and controls the magneticrecording/playing device 111 or still image recording medium 112 via thecamera signal processing circuit 108. Thus, suitable television signalsare provided to the recording medium, or in a case wherein the modeswitch 133 is set to the playing mode, playing control of the recordedtelevision signals from the magnetic recording/playing device 111 orstill image recording medium 112 is performed.

A computer zoom unit (control means) 119 that is within the cameramicrocomputer 116 outputs a signal to the zoom motor driver 122 by theprogram within the computer zoom unit 119 wherein the AF switch 131 isoff and the zoom switch 130 is operating, for driving the zoom lens unit102 in the telephoto or wide angle direction corresponding to theoperational direction of the zoom switch 130. The zoom motor driver 122receives this signal and drives in this direction of the zoom lens unit102 via the zoom motor 121. Further at this time, the computer zoom unit119 drives a focus motor 125 via a focus motor driver 126, based on thelens cam data (representative locus data or locus parameter dataaccording to the multiple subject distances, as illustrated in FIG. 11)previously stored in cam data memory 120, and drives the focus lens unit106 so as to correct the image movement that accompanies zooming.

Further, an AF control unit 117 in the camera microcomputer 116 drivesthe zoom lens unit 102 and focus lens unit 105 based on the distanceinformation to the subject (focus object) obtained from the output ofthe subject distance detecting circuit 127 or the AF evaluation signalthat is sent from the AF signal processing circuit 109, wherein the AFswitch 131 is on and the zoom switch 130 is operating, a variatingoperation is necessary to maintain the focus state, and therefore thecomputer zoom unit 119 sends also the lens cam data stored on the camdata unit 120 through the internal program.

Now, the output signal from the subject distance detecting circuit 127is calculated and processed at the distance information processing unit128 within the camera microcomputer 116, and is output to the computerzoom unit 119 as the subject distance information.

Further, in the event that the AF switch 131 is on and the zoom switch130 is not operating, the AF control unit 117 outputs a signal to thefocus motor driver 126 to drive the focus lens 105 so as to make the AFevaluation value signal sent from the AF signal processing circuit 109as great as possible, and drives the focus lens unit 105 via the focusmotor 125. Thus, the automatic focus adjusting operation is performed.

Here, the subject distance detecting circuit 127 measures the distanceto the subject with triangulation using an active sensor, and outputsthe distance information that is the measurement result thereof. Theactive sensor in this case can be an infrared sensor that is widely usedin compact cameras.

Now, the present embodiment is described with the example of performingdistance detection using triangulation, but other distance detectionmethods can also be used for the present invention. For example,distance detection with phase-difference detection can also be used. Inthis case, for example, an element (half prism or half mirror) isprovided to divide the light that passes through the exit pupil of theimage-taking lens (i.e., TTL (Through The Lens) method), the lightexited from this element is guided to no fewer than two line sensors viaa sub mirror or image forming lens, and by taking the correlation of theoutput of these line sensors, the offset direction and offset amount ofthese outputs can be detected, and the distance from these detectionresults to the subject is found.

A principal diagram of the distance calculation using triangulation orphase-difference detection is illustrated in FIG. 15 and FIG. 16. InFIG. 15, reference numeral 201 denotes a subject, 202 denotes an imageforming lens for a first optical path, 203 denotes a line sensor for thefirst optical path, 204 denotes an image forming lens for a secondoptical path, and 205 denotes a line sensor for the second optical path.The line sensors 203 and 204 are installed apart by the distance of abase line B. Of the light from the subject 201, the light that passesthrough the first optical path by the image forming lens 202 forms animage on the line sensor 203, and the light that passes through thesecond optical path by the image forming lens 204 forms an image on theline sensor 205. Here, FIG. 16 illustrates an example of the signalreadout from the line sensors 203 and 205 which have received the twosubject images formed by passing through the first and second opticalpaths. Because the two line sensors are apart by the distance of thebase line B, the subject image signal has only the offset of X number ofpixels, as shown in FIG. 15. Therefore the correlation of the twosignals can be calculated by offsetting the pixels, and X can becalculated by obtaining the amount of pixel offset wherein thecorrelation becomes greatest. Using the principle of triangulation, thedistance L to the subject can be obtained from L=Bxf/X, using this X andthe base line B, and the focal distance f of the image forming lens 202and 204.

Further, as a distance detection means, an ultrasound sensor may be usedto measure the propagation speed and detect the distance to the subject.

The distance information from the subject distance detecting circuit 127is sent to the distance information processing unit 128. The distanceinformation processing unit 128 performs the three types of processingbelow.

1. Calculates cam locus of which distance in FIG. 9 to which the zoomlens unit 102 and focus lens unit 105 positions correspond. Thecalculation for the cam locus outputs a virtual cam locus thatinternally divides the cam locus of the γ′th row and the γ′th+1 row ofthe row direction in FIG. 12 for the locus parameters α, β, and γ, bythe ratio of α/β, as the subject distance and to how many meters this isequivalent to, for example, as described in process S401 in FIG. 4A,based on the current lens unit position. The locus parameters α, β, andγ, and the subject distance are converted at the fixed correlation tabledata, and the actual distance of the main subject can be output.

2. By inverting the actual distance of the subject from the subjectdistance detecting circuit 127, using the correlation table mentionedabove in 1, the cam locus in FIG. 9 above that is denoted by the locusparameters α, β, and γ are found. At this time, the inverting process ofthe correlation table does not use the data from the wide angle sidewherein the cam loci in FIG. 9 converge, and the loci are scattered. Thedata from the telephoto side is used as much as possible, and locusparameters with the highest possible resolution.

3. The actual distance difference and the differential direction iscalculated for the above 1 and 2.

Of these processes 1, 2, and 3, the process 2 can identify the cam locusdata correlating to the detection distance detected with the subjectdistance detecting circuit 127.

On the other hand, the camera microcomputer 116 also performs exposurecontrol. The camera microcomputer 116 references the brightness level ofthe television signal formed in the camera signal processing circuit108, controls the iris driver 124 so as to make the brightness levelappropriate for exposure, and controls the opening of the aperturediaphragm 103. The opening amount of the aperture diaphragm 103 isdetected using an iris encoder 129, and feedback control of the aperturediaphragm 103 is performed. Further, in the case that sufficientexposure control cannot be performed with the aperture diaphragm 103alone, a timing generator (TG) 132 is used to control the exposure timeof the imaging device 106, which handles anywhere from a high speedshutter to a so-called slow shutter for extended exposure. Further, whenexposure is insufficient such as image-taking under low lighting, thetelevision signal gain is controlled using the amplifier 107.

By operating a menu switch unit 135, the photographer can manuallyoperate the image-taking mode or camera function switching appropriatefor the image-taking state.

Next, the algorithm during zooming operation will be described withreference to FIGS. 3A and 3B. With the present embodiment, the computerzoom unit 119 in the camera microcomputer 116 executes thebelow-described operation flow processes, including the aforementionedvarious operation flows (programs).

Further, with the present embodiment, the cam locus to be followed isidentified (formed) according to the distance information obtained fromthe subject distance detecting circuit 127, and zooming operation isperformed. The operation flow in FIGS. 3A and 3B is an example of amethod for zooming operation while establishing (producing) a zoomtracking curve which is the cam locus to be followed, using the distanceinformation. This method is particularly effective in the case that thedetection cycle of the AF evaluation value such as very high speed zoombecomes less fine, and sufficient contrast to establish the zoomtracking curve cannot be obtained from the TV-AF reference signal alone(AF evaluation value signal).

FIGS. 3A and 3B illustrate a process performed in S705 of FIG. 7 asdescribed previously, and where the processes (steps) are the same asthose in FIGS. 4A and 4B, the same reference numerals will be used andthe description thereof will be omitted.

In S400, the zoom speed during zooming operation is determined. In S300,the distance to which cam locus of the representative locus illustratedin FIG. 9 the current main subject image-taking distance corresponds tois determined, according to the output signal of the subject distancedetecting circuit 127, and the locus parameters α, β, and γ arecalculated. Further, in the same way, the locus parameters αnow, βnow,and γnow corresponding to the current zoom lens position and focus lensposition as described in S401 in FIG. 4A are calculated.

The αnow, βnow, and γnow are α, β, and γ calculated in the process fromS512 to S515 in FIG. 5 and stored in memory under the respective namesαnow, βnow, and γnow. On the other hand, the locus parameters based onthe distance information obtained from the subject distance detectingcircuit 127 are calculated as α, β, and γ using for example thefollowing method.

First, in order to obtain the correlation between the output distanceinformation and the representative locus (cam locus) illustrated in FIG.9, the correlation between the distance change and the locus parametersare placed in a table data form in advance, within the range wherein thecam loci (cam curve) form of the representative subject distance isuniform. Therefore, the locus parameters are calculated using thedistance information as input. As for the subject distance wherein thecam loci form changes, a lookup table is provided that shows a separatecorrelation, and having these multiple tables enables the locusparameters for each of the subject distances to be obtained.

Regarding the focal distance, of the discrete cam locus information inFIG. 9 that is within the memory as data, the locus parameters at thelong focal distance side can be output so as to make the greatestresolution of the locus parameters α, β, and γ. Therefore, even if thecurrent lens position is at the position wherein the cam loci areconverging at the wide angle side as illustrated in FIG. 9, the locusparameters can be extracted at the point on the telephoto side whereinthe cam loci are scattered, according to the distance information.Therefore, at the point wherein the zoom lens 102 is positioned on thewide angle side, one cam locus upon which the focus lens 105 shouldtravel can be identified by calculating (interpolating) based on thelocus parameters on the telephoto side.

Now, S300 is executed every certain cycle (for example, one verticalsynchronizing signal). Therefore, even if the subject distance changesduring zooming, the newest cam locus to follow is continuously updatedaccording to the output of the subject distance detecting circuit 127.

Next, in S301, the correction range of the cam locus, which is a featureof the present invention, is determined based on the output of thesubject distance detecting circuit 127 (in other words, α, β, andγcalculated in S300). This correction range is equivalent to thecorrection range in the correction operation for the following cam locuswherein the TV-AF signal (AF evaluation value), and may be, for example,the range between the upper limit 201 and the lower limit 202illustrated in FIG. 2.

Here, according to the present embodiment, when the output from thesubject distance detecting circuit 127 for example corresponds to thesubject distance of 5 m (203), the correction range is controlled to bea range of ±50 cm of that subject distance. In other words, the upperlimit 201 is a cam locus equivalent to corresponding with a subjectdistance of 4.5 m, and the upper limit 202 is a cam locus equivalent tocorresponding with a subject distance of 5.5 m. Now, this correctionrange should be determined according to the detection sharpness of thesubject distance detecting circuit 127.

In other words, the aforementioned correction range is set so as tocontrol the re-generating range when performing precise re-generating ofthe following cam locus by the correction operation (zigzag operation)by the TV-AF signals, after a general following cam locus is specifiedbased on the distance information from the subject distance detectingcircuit 127.

Thus, the detecting resolution (detecting accuracy) of the subjectdistance detecting circuit 127 does not have to be so high, and as aresult, a smaller imaging device can be provided at a lower cost. Inaddition, due to restricting the correcting range of the following camlocus, the number of times of directional switching when re-identifyingthe following cam locus using the TV-AF signal can be increased, and dueto reducing the frequency of continuing to correct in the samecorrection direction, the occurrence of blurring can be preventedwherein perfect focus and image blurring were cyclically repeatedaccording to the zigzag operation in the cases of image-taking a subjectwith a high frequency. Further, image blurring in the case of followingan incorrect following cam locus or image blurring when recovering tothe correct cam locus can be reduced.

Regarding the actual operation, the correction operation (zigzag drive)of the following cam locus using the TV-AF signal is performed withinthe range between the upper limit 201 and the lower limit 202, and inthe case of deviating from this range, the focus lens 105 drivedirection is reversed so as to return to this correction range. As aresult, re-generating of the cam locus outside the range of the upperlimit 201 and the lower limit 202 is prohibited.

According to the present embodiment, the correction range is setaccording to the detection resolution of the subject distance detectingcircuit 127, and by allowing generating of the precise following camlocus by the TV-AF signal only within that range, erroneous movementresulting from dual use of the TV-AF signal or erroneous image blurringis reduced. In other words, by allowing re-generating of the followingcam locus only when the generating results of the two types of cam locusgenerating methods agree, which are the generating method of a cam locusbased on the output from the subject distance detecting circuit 127 andthe generating method of a cam locus based on the detecting signal atthe focus state of the TV-AF signal, an extremely highly precise camlocus following method can be realized by combining only the strengthsof each generating method.

Specifically, when identifying the following locus by the TV-AF signalas described in the conventional art, the focus lens drive speed(correction speed) for the zigzag operation needed to be set to a speedcapable of covering from the cam locus on the infinity side to the camlocus on the close-up side. In comparison, according to the presentembodiment, by limiting the correction range of the cam locus, forexample even if the focus lens correction speed is the same as theconventional art, the drive range has become narrower, and so the numberof zigzag operations can be increased for each unit of time. Therefore,even at a high speed zoom, the cam locus generating precision by theTV-AF signal can be improved.

On the other hand, the setting value of the correction speed can belowered by having the normal number of zigzag operations, the occurrenceof blurring can be prevented wherein focusing and image blurring werecyclically repeated according to the correction operation whenimage-taking a subject with a high frequency (details will be describedin the second embodiment). Therefore, an imaging device zooming systemthat has a high degree of freedom for implementing zoom functionalitywith the best control method according to the product use can beprovided, such as priority for zoom speed or priority for appearance,even though using the same method. This is an addition advantage of thepresent embodiment and the present invention.

Returning to the description of FIGS. 3A and 3B, in S302 whether or notthe “AF correction flag” is in the set state is determined. If set, theflow continues to S303, and in S311, which will be described below,whether or not the locus parameters αAF, βAF, and γAF, which are updatedwith each detection that the AF evaluation value reaches the peak state1301 level described in FIG. 13, are included in the correction range(the range between the upper limit 201 and the lower limit 202)illustrated in FIG. 2, is determined. If within this correction range,S304 sets each of these αAF, βAF, and γAF, to α, β, and γ, and controlsthe focus lens 105 to trace the cam locus re-specified by thiscorrection movement.

On the other hand, in the case that the locus parameters αAF, βAF, andγAF, are outside the correction range in S303, or in the event that the“AF correction flag” has been cleared in S302, the locus parameters α,β, and γ, that are specified based on the distance information from thesubject distance detecting circuit 127, that were already decided inS300, are held, and the focus lens 105 is controlled to trace the camlocus specified by these locus parameters α, β, and γ.

Here, the “AF correction flag” is a flag showing whether or not thefollowing cam locus has been re-specified by the later-described TV-AFsignal, and in the case that generating is made based only on thedistance information from the subject distance detecting circuit 127 (inthe case where re-generating is not performed, or in the case that thecam locus is outside the correction range in FIG. 2 and the possibilityof erroneous generating is high), in S305 the “AF correction flag” iscleared, and from the next time and thereafter, until the re-generatingof the cam locus by the correction movement is performed, the locustrace control is performed giving priority to the generating resultsbased on the distance information.

Hereafter, a process similar to that in FIGS. 4A and 4B is performed. InS402 the position Z_(x)′ (the position to which it should move from thecurrent position) wherein the zoom lens 102 will arrive after onevertical synchronizing period (1V) is calculated. In the event that thezoom speed determined in S400 is Zsp (pps), the zoom lens positionZ_(x)′ after one vertical synchronizing period can be obtained from theabove-described Equation (7). Here, pps is an increment that shows therotation speed of the stepping motor which is the zoom motor 121, andrepresents the step amount (1 step=1 pulse) of rotation during 1 second.The symbols in Equation (7) represent the movement direction of the zoomlens, + for the telephoto direction and − for the wide angle direction.Z _(x) ′=Z _(x) ±Z _(sp)/vertical synchronizing frequency  (7)

Next, in S403, which zoom area v′Z_(x)′ exists is determined. In S403,the same process as the process illustrated in FIG. 6 is performed, andZ_(x) in FIG. 6 is substituted with Z_(x)′, and v with v′.

Next, in S404, whether the zoom lens position Z_(x)′ after one verticalsynchronizing period exists on the zoom area boundary is determined, andin the event that the boundary flag=0 this it not considered to be onthe boundary, and the flow continues from the process starting withS405. In S405, Z_((v′)) is set to Z_(k), and Z_((v−1)) to Z_(k−1).

Next, in S406, out the four table data sets A_((γ, v′−1)), A_((γ, v′)),A_((γ+1, v′−1)), A_((γ+1, v′)) wherein the subject distance γ isspecified by the process illustrated in FIG. 5 are read out, and a_(x)′and b_(x)′ are calculated from the Equations (2) and (3) described abovein S407.

On the other hand, in the case of Yes in S403, in S408 the focus lenspositions A_((γ, v′)) and A_((γ+1, v′)) corresponding to the zoom areav′ of the subject distance y are called up and stored in memory asa_(x)′ and b_(x)′, respectively. Then, in S409 the focus lens focusposition (target position) p_(x)′ when the zoom lens position hasreached Z_(x)′ is calculated. Using Equation (1), the target position ofthe focus lens 105 after one vertical synchronizing period can beexpressed as follows.P _(x)′=(b _(x) ′−a _(x)′)×α/β+a _(x)′  (8)

Therefore, the difference of the target position and the current focuslens position becomesΔF=(b _(x) ′−a _(x)′)×α/β+a _(x) ′−P _(x)

Next, S410 calculates the focus standard moving speed V_(f0). V_(f0) isobtained by subtracting the focus lens position difference ΔF from themovement time of the zoom lens 102 required to move this distance.

After completing the present process, the flow continues to S706 in FIG.7, and in the event that zooming is being performed, movement is made atthe focus speed determined in S410 in the direction of the symbol(positive for the close-up direction, and negative for the infinitedistance direction) of this focus speed, thereby carrying outcompensator actions.

In S411, each parameter is initialized. Here, the “reversal flag” usedin the later processes is cleared. In S412 the correction speed V_(f+)and V_(f−) is calculated for the “zigzag correction operation” from thefocus standard movement speed V_(f0) obtained in S410. Here, thecorrection amount parameter δ and the correction speeds V_(f+) andV_(f−) are calculated using Equations (9) through (12) as describedabove, using FIG. 14.

In S413, whether or not zooming is being performed is determined,according to the information illustrating the operational state of thezoom switch 130 obtained during S703 illustrated in FIG. 7. In the eventhat zooming is being performed, the process from S416 on is carriedout. Otherwise, in S309 the “AF correction flag is cleared, andpreparation is made for the next zooming operation from the wide angleto the telephoto direction. Then in S414, a value TH1 (the levelindicated by 1302 in FIG. 13A) is set, wherein a arbitrary constant μ issubtracted from the current value of the AF evaluation signal level.This TH1 determines the AF evaluation signal level that is theswitchover base point for the correction direction vector (switchoverbase point for the zigzag correction operation), as described in FIG.13A.

Next, in S415 the “correction flags” are cleared, and the process ends.Here, the “correction flag” is a flag indicating either a state whereinthe cam locus following state is when the correction is in the positivedirection (correction flag=1) or a correction state in the negativedirection (correction flag=0), as described above.

If determination is made in S413 that zooming is being performed,determination is made whether or not the zooming direction is from wideangle to telephoto in S414. If No, the “AF correction flags” are clearedand preparation is made for the next wide angle to telephoto directionzooming operation to be performed (S308), similar to S309. Then at S419,V_(f+)=0 and V_(f−)=0 are set, and the process from S420 is performedand zigzag drive is not executed.

If Yes in S413, in S306 determination is made whether or not the focuslens position in relation to the current zoom lens position surpassesthe upper limit 201 of the correction range illustrated in FIG. 2. Ifso, the flow continues to S423 to return the focus lens position towithin the correction range.

In S423, the calculated focus speed (standard movement speed) V_(f0) isadded to the negative correction speed V_(f−) (corrected to the infinitedistance direction). By doing so, the focus lens 105 is forced to returnto the direction of the lower limit 202 rather than the upper limit 201of the correction range.

Further, in the event that the upper limit 201 has not been exceeded inS306, determination is made in S307 whether or not the focus lensposition relating to the current zoom lens position is below the lowerlimit 202 of the correction range in FIG. 2. If so, the flow continuesto S423 to return the focus lens position to within the correctionrange. In S423, the calculated focus speed (standard movement speed)V_(f0) is added to the positive correction speed V_(f+) (corrected tothe close-up direction). By doing so, the focus lens 105 is forced toreturn to the direction of the upper limit 201 rather than the lowerlimit 202 of the correction range. Thus, the drive range of the focuslens 105 is controlled within the correction range, and as a result, thecam locus re-specified by the zigzag movement is also controlled withinthis correction range.

In the event that the focus lens position in S306 or S307 is not outsidethe correction range, determination is made in S417 whether or not thecurrent AF evaluation signal level is smaller than TH1, in order toexecute the zigzag movement. If Yes, the current AF evaluation level hasmoved lower than the level of TH1 (1302) in FIG. 13A, and therefore S418sets a reversal flag to perform switching of the correction direction.

Determination is made in S420 whether the reversal flag=1, and if Yes,the flow continues to S421 and determination is made whether thecorrection flag is 1 or not. If S421 yields No, then the flow continuesto S424 and sets the correction flag to 1 (correction state in thepositive direction). According to Equation (4),Focus speed V _(f) =V _(f0) +V _(f+) (wherein V _(f+)≧0)

On the other hand, in the event that S421 is Yes, then the flowcontinues to S423 and sets the correction flag=0 (correction state inthe negative direction), and according to Equation (5),Focus speed V _(f) =V _(f0) +V _(f−) (wherein V _(f−)≦0)

If S420 is determined to be No, S422 determines whether or not thecorrection flag=1. If Yes the flow continues to S424, and if No, theflow continues to S423.

After completing this process, in S706 in FIG. 7 the drive direction anddrive speed of the focus lens 105 and zoom lens 102 are selected,according to the operation mode.

In the case of a zooming operation, the focus lens 105 drive directionis set to the close-up direction or the infinite distance directiondepending on whether the focus lens movement speed V_(f) obtained inS423 or S424 is positive or negative. Thus, the cam locus to be tracedis re-specified as the focus lens 105 zigzag drive is performed.

During the process from S417 through S424 while performing the zigzagdrive, the AF evaluation value signal is detected to have reached thepeak level 1301 described in FIG. 13A. When S417 is No, S310 determineswhether or not the peak level 1301 is detected. In the case that thepeak level is detected, in S311, with the “AF correction flag=1” and thecurrent values of the locus parameters as re-generating locus parametersby TV-AF,αAF←αnow, βAF←βnow, γAF←γnowis set. Then, the next time that the conditions are fulfilled in S302and S303 (in the case that the determination results of both steps areYes), in S302 the identified cam locus is updated.

This time, the locus parameters updated and re-specified in S304 areupdated to the specified cam locus based on the distance information, bythe correction range in S301 changing by the change of the detecteddistance information, or by the zooming operation stopping, or by thezooming direction reversing.

In the case that the next time the conditions are not fulfilled in S302and S303, each time a new peak level is detected (S310), the updating ofαAF, βAF, and γAF is repeated and the most appropriate cam locus iscontinuously updated during zooming operation.

Now, in the case that the AF evaluation value level is not detected tohave reached the peak level in S310, the flow continues on to S420, andwithout switching the correction direction by the zigzag operation,drives the focus lens 105 whiles correcting in the correction directionpredetermined by the previous time.

By performing the above processes, the cam locus generating accuracyusing the TV-AF signal can be greatly improved by limiting theidentification range (correction range) in the case of identifying thecam locus to be followed using the TV-AF signal, based on the distanceinformation to the subject. Therefore, problems such as disadvantagesthat accompany the detection cycle of the AF evaluation value withTV-AF, or problems that erroneously determine the wrong cam locus to betraced because of influence the TV-AF signal receives not only from thedistance change but also from a change in the appearance of subject, orerroneous movement problems wherein the switching timing is incorrectfor the zigzag movement, can be reduced. Therefore, the occurrence ofimage blurring can be reduced.

Specifically, the cam locus to be the standard in the distanceinformation is specified, and by using the method of the presentembodiment wherein the correction range is limited and the cam locus iscorrected (re-specified) using the TV-AF signal, the correctionresolution of the following cam locus based on the TV-AF signal can beimproved. Therefore, the detecting resolution of the subject distancedetecting circuit 127 does not need to be so fine, and a smaller andless costly type of subject distance detecting circuit 127 can beemployed.

Second Embodiment

The first embodiment has been described regarding a case in which thecorrection speed of the correction movement for the focus lens 105 bythe TV-AF signal is calculated in the same way as with the conventionalart described in FIGS. 4A and 4B. Because of this, in the firstembodiment, the movement distance (drive range) of the focus lens 105 islessened because of the limits on the correction range, and as a result,the frequencies of the zigzag operation within the correction rangeincreases. Therefore, a system is provided wherein the generatingfunctionality of the following cam locus is high, even at a high speedzoom and so forth.

In contrast, according to the second embodiment, the correction speed isset slower than in the case of the first embodiment, and attempts toreduce the cyclical image blurring that accompanies the zigzag movementand so forth.

For example, if the correction speed is set at half the amount of thefirst embodiment, the overshooting amount of the drive direction reversetiming of the focus lens 105 illustrated in FIG. 13B is reduced, andtherefore the type of phenomenon wherein focusing and image blurring arecyclically repeated according to the zigzag operation can be preventedfrom occurring.

In order to change the correction speed to ½, the process wherein thecorrection speed V_(f+) and V_(f−) is calculated in S412 illustrated inFIGS. 3A and 3B is cut in half may be added, for example. Further,computations can be made by providing a coefficient to Equations (4) and(5).Focus speed V _(f) =V _(f0) +V _(f+)/2 (wherein V _(f+)≦0)  (4)′Focus speed V _(f) =V _(f0) +V _(f−)/2 (wherein V _(f−)≦0)  (5)′

Now, the aforementioned embodiments have been described regarding a caseof controlling the range for when the cam locus (α, β, γ) to be followedis identified (generated) based on the distance information to thesubject, but the present invention may also be applied in the case ofcontrolling the range based on the distance information to the subject,when the focus lens target position is calculated (generated).

As described in the first embodiment and the second embodiment, therange of information (locus information and so forth) that is generatedto control the drive of the second lens unit, based on the distance tothe detected focus object, is limited, and therefore can avoid producinginformation that does not correspond to the distance to the object forwhich focus is actually desired, and image blurring during zooming canbe reduced.

Here, the aforementioned information is generated based on the distanceto the focus object detected and the aforementioned data, and as a basisfor this aforementioned generated information, and in the case ofperforming forming processing wherein new information is generated usingthe focus signal representing the focus state of the optical systembased on this detected distance in the event that the range ofinformation generated by this forming process is limited, problems suchas disadvantages that accompany the detection cycle of the focus signal,or problems wherein incorrect information is generated because ofinfluence the focus signal receives, not only from the distance changebut also from change in the appearance of the focus object, or erroneousmovement problems wherein the switching timing is incorrect for thezigzag movement, can be avoided, and the occurrence of image blurringduring the forming process can be reduced, and focus maintenance controlwith high precision during zooming can be performed.

Further, in the re-generating process, in the case of changing thedriving conditions of the lens unit to move this second lens unittowards the position wherein the focus signal represents the mostfocused state corresponding to the drive state when driving based onthis aforementioned standard information, the second lens unit driverange is limited based on the detected distance, and by doing so, thesecond lens unit can avoid driving based on incorrect information. Inaddition, even in the case wherein the switching timing of the zigzagmovement is wrong, the image blurring amount can be reduced, and canquickly make transition to driving based on the correct information.

Third Embodiment

The zigzag movement disclosed in the aforementioned Japanese Patent No.2,795,439 specifies the following locus based on the change of the AFevaluation value. However, the evaluation value changes not onlyaccording to the status of blurring of the image, but also changesaccording to changes in appearance of the subject. Therefore, there maybe a case wherein the focus lens movement switching is switched in thewrong direction. In the event that the movement deviates from the locusthat should be used, the image may blur until moved back to the correctlocus. Further, in the case of moving the focus lens in the wrongdirection, image blurring may occur wherein the AF evaluation valuelevel in particular is greatly reduced, or when image-taking of asubject with low contrast, the correct locus may not be found, and thepossibility exists that the image blur may be carried all the way to thetelephoto edge.

Specifically, when starting zooming from the wide angle side wherein thecam locus spacing is crowded, if the drive starting direction by thezigzag driving is in the opposite direction from the direction of thecam locus (focus locus) to be specified, the image blurring isnoticeable even if the offset from the position of the focus locus issmall because the focus depth is shallow at the wide angle side.Further, as described above, on the wide angle side wherein the subjectsfrom infinity to several 10 cm away are all focused on at the same focusposition, in the event that multiple objects with differing subjectdistances exist within the wide angle, the image of these subjects allbecome blurred, and the quality of the image becomes very poor.

The algorithm during zooming operation will be described with referenceto FIGS. 17 and 18. According to the present embodiment, the computerzoom unit 119 in the camera microcomputer 116 executes thelater-described operation flow processes, including the aforementionedvarious operation flows (programs). Now, in FIGS. 17 and 18, theportions indicated by the same circled numeral are connected to oneanother.

Further, according to the present embodiment, the cam locus to befollowed is established (formed) according to the distance informationobtained from the subject distance detecting circuit 127, and zoomingoperation is performed. The operation flow shown in FIGS. 4A and 4B isan example of a method as described above for zooming operation whileprecisely establishing (generating) a zoom tracking curve which is thecam locus to be followed, using the distance information. This method isparticularly effective for recovering image blurring in the case thatthe focus lens 105 is moved off the focus cam locus during zooming, orreducing image blurring at the start of the zooming operation.

FIGS. 17 and 18 are processes performed in S705 of FIG. 7 as describedpreviously, and wherein the processes (steps) are the same as those inFIGS. 4A and 4B, the same reference numerals will be used and thedescription will be omitted.

In S1400, the zoom speed during zoom operation is determined. In S1401,which position on the cam locus in FIG. 9 the main subject beingphotographed is, is determined, from the current zoom lens position andthe focus lens position. Here, from the interpolation process based onthe cam locus data table (FIG. 12) storing the representative locusillustrated in FIG. 9 as discrete data, the cam locus where the currentzoom lens and focus lens positions exist, including virtual cam locus,in other words three locus parameters that correspond to this cam locusare calculated as α, β, and γ, and are stored in a memory region such asRAM. This process is the same process as that described with referenceto FIG. 5.

In S1300, the calculated locus parameters α, β, and γ are temporarilysaved as αnow, βnow, and γnow, and additionally the locus parameters α,β, and γ are calculated regarding how many meters in actual the subjectdistance (estimated distance). The correlation between the locusparameters and the estimated distance can be calculated by creating inadvance a table data of the correlation between the estimated distanceand the locus parameter within the range wherein the cam curve form ofthe representative subject distance is uniform, with the locusparameters as input. At a subject distance wherein the cam curve formchanges, a lookup table can be made to show different correlations, andby having these multiple tables, all of the estimated distances B can beobtained for each zoom lens position and focus lens position.

Next, in S1301, the output from the subject distance detecting circuit127 is obtained. Then, the distance to the image-taking subject shown bythe output from the subject distance detecting circuit 127 (actualdistance) A is compared with the estimated distance B found from thecurrent lens position in S1300, and determination is made whether theactual distance A is nearer (close-up direction) or farther (infinitydistance direction) as compared to the estimated distance B.

Next, determination is made in S1302 whether or not the “AF correctionflag” is in the set state. If set, the flow continues to S1303, and thelocus parameters αAF, βAF, and γAF to be decided in the following S1311are set as α, β, and γ respectively (stored in memory). Here, thechanges in the AF evaluation signal are detected while performing thezigzag operation of the focus lens unit 105, and the locus parametersαAF, βAF, and γAF are the cam locus parameters when at the peak level1301 in FIG. 13A. In other words, these are the cam locus informationdetected by the AF evaluation signal peak level, and represent the camlocus that the microcomputer 116 has confirmed as the true focus camlocus.

Thus, the locus parameters α, β, and γ that are updated in S1303represent the cam locus re-specified based on the AF evaluation signal,and by continuing to perform re-specification of the cam locusrepeatedly with a continuous zooming operation thereafter, the result isthat the focus lens unit 105 can be made to trace (follow) the truefocus cam locus.

On the other hand, in the event that the “correction flag” is cleared inS1302, the locus parameters α, β, and γ specified based on the distanceinformation from the subject distance detecting circuit 127 that havealready been decided in S1300 are held, and the focus lens 105 iscontrolled to trace the cam locus specified by these locus parameters α,β, and γ.

Here, the “correction flag” is a flag showing whether or not the camlocus to be followed has been re-specified by the below described AFevaluation signal, and once set (when the following cam locus isre-specified), it will not be cleared unless the zooming direction isswitched or the zooming operation is stopped. The re-specified cam locusinformation (α, β, and γ) is re-specified (updated) continually based onthe detection results of the AF evaluation signal, and at the focaldistance wherein the cam loci are scattered, identified on the focuslocus.

Hereafter, a process similar to that in FIGS. 4A and 4B is performed. InS1402, the position Z_(x)′ (the position to move to from the currentposition) where the zoom lens 102 will arrive after one verticalsynchronizing period (1V), is calculated. In the event that the zoomspeed determined in S400 is Zsp (pps), the zoom lens position Z_(x)′after one vertical synchronizing period can be obtained from theabove-described Equation (7). Here, pps is an increment that shows therotation speed of the stepping motor which is the zoom motor 121, andrepresents the step amount (1 step=1 pulse) of rotation during 1 second.The symbols in Equation (7) represent the movement direction of the zoomlens, + for the telephoto direction and − for the wide angle direction.Z _(x) ′=Z _(x) ±Zsp/vertical synchronizing frequency  (7)

Next, in S1403, which zoom area v′ where Z_(x)′ exists is determined.S1403 is the same process as the process illustrated in FIG. 6, and theZ_(x) in FIG. 6 is substituted with Z_(x)′, and v with v′.

Next, determination is made in S1404 whether the zoom lens positionZ_(x)′ after one vertical synchronizing period exists on the zoom areaboundary, and if the boundary flag=0 is it not considered to be on theboundary, and the flow continues from the process starting with S1405.In S1405 Z_((v′)) is set to Z_(k), and Z_((v′−1)) to Z_(k−1).

Next, in S1406 the four table data sets A_((γ, v′−1))′, A_((γ, v′)),A_((γ+1, v′−1))A_((γ+1, v′)) wherein the subject distance y is specifiedby the process illustrated in FIG. 5 are calculated, and a_(x)′ andb_(x)′ are calculated from the Equations (2) and (3) described above inS1407.

On the other hand, in the case that S1403 is determined to be Yes, inS1408 the focus lens positions A(γ, v′) and A(γ+1, v′) corresponding tothe zoom area v′ of the subject distance y are called up and stored inmemory as a_(x)′ and b_(x)′, respectively. Then, in S1409 the focus lensfocus position (target position) p_(x)′ when the zoom lens position hasreached Z_(x)′ is calculated. Using Equation (1), the target position ofthe focus lens 105 after one vertical synchronizing period can beexpressed as follows.P _(x)′=(b _(x) ′−a _(x)′)×α/β+a _(x)′  (8)

Therefore, the difference ΔF of the following target position and thecurrent focus lens position becomesΔF=(b _(x) ′−a _(x)′)×α/β+a _(x) ′−P _(x)

Next, in S1410 the focus standard moving speed V_(f0) is calculated.V_(f0) is obtained by subtracting the focus lens position difference ΔFfrom the movement time of the zoom lens 102 required to move thisdistance.

After completing the present process, the flow continues to S706 in FIG.7, and if zooming is being performed, moves at the focus speeddetermined in S1410 in the reference numeral direction (positive for theclose-up direction, and negative for the infinite distance direction) ofthis focus speed, thereby performing compensator actions.

In S1411, each parameter is initialized. Here, the “reversal flag” usedin the later processes is cleared. In S1412 the correction speed V_(f+),V_(f−) for the “zigzag correction operation” is calculates from thefocus standard movement speed V_(f0) obtained in S1410. Here, thecorrection amount parameter δ and the correction speeds V_(f+), V_(f−)are calculated using Equations (9) through (12) as described above withFIG. 14.

Determination is made in S1413 whether or not zooming is beingperformed, according to the information representing the operationalstate of the zoom switch 130 obtained during S703 in FIG. 7. If zoomingis being performed, the process from S1416 is performed. If Yes theprocess from S1416 is performed. If No is determined, in S1313 the “zoomflag” and the “correction flag are cleared, and preparation is made forthe next zooming operation from the wide angle to the telephotodirection. Then at S1414, a value TH1 (the level denoted by 1302 in FIG.13A) is set, wherein a arbitrary constant μ is subtracted from thecurrent value of the AF evaluation signal level. This TH1 is decidedimmediately prior to zooming, and this value is the level of 1302 inFIG. 13A.

Next, S1415 clears the “correction flags”, and ends this process. Here,the “correction flag” is a flag denoting either a state wherein the camlocus following state is when the correction is in the positivedirection (correction flag=1) or a correction state in the negativedirection (correction flag=0), as described above.

In the event that determination is made in S1413 that zooming is beingperformed, determination is made whether or not the zooming direction isfrom wide angle to telephoto in S1414. If No, the “correction flags” arecleared and the preparation is made for the next wide angle to telephotodirection zooming operation to be performed (S1312), similar to S1313.Then at S1419, V_(f+)=0 and V_(f−)=0 are set, and the process from S1420is performed and zigzag drive is not executed.

If S1413 is Yes, determination is made in S304 whether or not the “zoomflag” is in the cleared state. If cleared, the flow continues to S1305because this is the first case wherein zooming is from the wide angle tothe telephoto direction, the “zoom flag” is set, and further, so as tocorrectly match the correction direction (the drive start direction ofthe focus lens unit 105) of the zigzag movement based on the detectingresult of the AF evaluation signal at zoom start time with the objectdistance direction of the main subject, determination is made in S1306whether the distance information obtained from the output of the subjectdistance detecting circuit 127 is in the close-up direction or in theinfinite distance direction compared to the distance corresponding tothe current focus lens position.

Here, the process of S1306 is to determine the relationship between theestimated distance B that is based on the lens position determined inS1300, and the actual distance A that is based on the output of thesubject distance detecting circuit 127 determined in S1301. In the casethat the actual distance A is on the closer side of the estimateddistance B, in other words, in the case that it is towards the close-updirection, the flow continues to S1424, and starts the zigzag movementcorrection in the correction direction of the close-up direction. In thecase that S1306 is No, in other words the actual distance A is on thefarther side of the estimated distance B, the flow continues to S1423 inorder to start the correction movement from the infinite distancedirection.

Thus, the present embodiment has a first feature wherein at the point ofstarting the zooming, the correction direction for the generatingmovement of the cam locus using the AF evaluation signal sets thedistance corresponding to the focus lens unit 105 position (estimateddistance B) so as to be closer to the distance (actual distance B) thatis based on the output of the subject distance detecting circuit 127, inother words sets weighting relating to the drive direction of the focuslens unit 105.

By performing this type of movement, a phenomenon can be avoidedwherein, when starting zooming from the wide angle side wherein the camlocus spacing is crowded, the drive starting direction of the focus lensunit 105 during zigzag operation moves in the opposite direction fromthe direction of the focus cam locus, which causes the image blurring tobe conspicuous even if the offset from the position of the focus locusis small because the focus depth is shallow. Therefore, in the case thatthe focus cam locus direction at the wide angle and the focus lens unit105 drive direction (correcting direction) is in the opposite direction,the problem wherein the images of objects with differing subjectdistances the image of these subjects all become blurred and the qualityof the image becomes very poor can be prevented in advance.

The description will be continued from S1304. Once the “zoom flag” isset in S1306, the flow continues to S1307 based on the determinationresults at S1304 (zoom flag=1) from the next time. As with S1306,determination is made in S1307 whether or not the distance informationbased on the output of the subject distance detecting circuit 127(actual distance A) is closer than the estimated distance B. If Yes,S309 sets V_(f+) at twice the value, to give priority weighting to theclose-up direction of the zigzag movement. On the other hand, in thecase that S1307 is No, the flow continues to S1308, and adds weightingby doubling V_(f−). This is a second feature of the present embodimentwherein weighting is added to the correcting movements for re-generatingof the cam locus using the AF evaluation signal, based on the detectedactual distance A (according to the relationship between the actualdistance A and the estimated distance B).

Because of this weighting correction process, for example, whenidentifying the cam locus based on the changes in the AF evaluationsignal, not only does the AF evaluation signal change due to the imageblurring state, but also changes due to the changes in the design of thesubject, and therefore, the problem of the correction direction beingincorrectly switched (problems such as the image blurring continuing fora long time until returning to the correct locus, or the image blurringbeing carried all the way to the telephoto edge) can be avoided.

As one example of the weighting process, the present embodimentdescribed the case wherein the focus lens unit 105 drive speed(correction speed) for the correction process is doubled, based on thedetected actual distance A, but the present invention does not need tobe limited to this. For example, the weighting ratio of the correctionspeed can be changed according to the difference between the detectedactual distance A and the estimated distance B based on the lensposition and the direction thereof.

Further, rather than increasing the correction speed in the directionmoving closer to the actual distance A, the correction speed in theopposite direction may be decreased.

Further, the AF evaluation value switching level (TH1) 1302 shown inFIG. 13A as a condition for switching the correction direction can beset low in the direction moving closer to the focus lens positioncorresponding to the actual distance A, and this level 1302 set high inthe correction direction that moves away from the focus lens positioncorresponding to the actual distance A, whereby the frequency ofcorrection operations in the direction moving closer to the focus lensposition corresponding to the actual distance A can be increased.

Thus, zigzag operation is executed by performing the processing afterS1417 while performing the weighting process of the zigzag operationbased on the detected distance information during zooming operation.First, S1417 determines whether or not the current AF evaluation signallevel is smaller than TH1. If Yes, then in S1418 a reversal flag is setto perform correction direction switching, since the current AFevaluation signal level has become lower than the TH1 (1302) level inFIG. 13A.

In S1420, determination is made whether the reversal flag=1, and if Yes,the flow continues on to S1421 where determination is made whether thecorrection flag is 1 or not. If No in S1421, the flow continues toS1424, and sets the correction flag to 1 (the correction state in thepositive direction). Based on Equation (4),Focus speed V _(f) =V _(f0) +V _(f+) (wherein V _(f+)≧0).

On the other hand, if S1421 is Yes, the flow continues to S1423, andsets the correction flag to 0, (the correction state in the negativedirection), and based on Equation (4),Focus speed V _(f) =V _(f0) +V _(f−) (wherein V _(f−)≦0)

In the case that S1420 is determined to be No, determination is madewhether or not the correction flag is 1 at S1422, and if Yes the flowcontinues to S1424, and if No, to S1423.

After completing this process, in S706 in FIG. 7, the direction anddrive speed of the focus lens and zoom lens drive are selected,according to the operation mode.

In the case of zooming operation, here the focus lens 105 drivedirection is set to the close-up direction or the infinite distancedirection, depending on whether the focus lens movement speed V_(f)obtained in S1423 or S1424 is positive or negative. Thus, the cam locusto be traced is re-specified while the focus lens 105 zigzag drive isperformed.

During the process from S1417 through S1424 while performing the zigzagdrive, the AF evaluation value signal is detected to have reached thepeak level 1301 described in FIG. 13A. In the event that S1417 is No,determination is made in S1310 regarding whether or not the peak level1301 has been detected. In the case that the peak level has beendetected, in S1311, with the “AF correction flag=1” and the currentvalues of the locus parameters as re-generating locus parameters byTV-AF,αAF←αnow, βAF←βnow, γAF←γnowis set. Then, the next S1302 determines the “correction flag=1”, and soin S1303 the generating cam locus is updated.

This time, as long as the zooming operation does not stop or the zoomingdirection does not reverse, the locus parameter updated and re-specifiedin S1303 repeats the updating of αAF, βAF, γAF in S1311 each time a newpeak level is detected (S1310), and the optimal cam locus is constantlyupdated during zooming operations.

Now, in the case that the AF evaluation value level is not detected tohave reached the peak level in S1310, the flow continues on to S420, andwithout switching the correction direction by the zigzag operation,drives the focus lens 105 whiles correcting in the correction directionpredetermined by the previous time.

According to the present embodiment as above, weighting settings basedon the detected distance information are made relative to the drivestart direction of the focus lens unit 105 in the zigzag movement, andtherefore the occurrence of image blurring during the zigzag operationcan be reduced.

In addition, the possibility exists of the main subject changingdistance during zooming operation, but according to the presentembodiment, the cam locus can be changed over quickly and smoothlybecause weighting is added to the drive or drive speed in the directionmoving closer to the focus lens position corresponding to the detecteddistance. Further, even in the event wherein the focus lens unit 105 isdriven in the wrong direction by the correction movement from the AFevaluation signal, moving away from the correct cam locus that it shouldbe following, the occurrence of image blurring can be reduced, andreturning smoothly to the correct cam locus is enabled.

Further, using the methods according to the present embodiment enablesthe generating precision of the following cam locus based on the TV-AFsignal (AF evaluation signal) to be improved. Therefore, the detectingprecision of the subject distance detecting circuit 127 can be somewhatless fine, and a smaller and less costly type of subject distancedetecting circuit 127 can be employed.

Therefore, according to the present embodiment, at the time ofcontrolling the second lens drive to generate the aforementionedinformation (locus information and so forth), weighting is performedbased on the distance to the detected focus object, and therefore, thedriving of the second lens unit which would make the image blurringgreater can be reduced. For example, relating to the drive direction ofthe second lens unit for generating the aforementioned information,weighting based on the detection results of the aforementioned distanceenables driving toward the direction in which the image blurring of thesecond lens unit increases to be avoided. Further, relating to the drivedirection of the second lens unit for generating the aforementionedinformation, weighting based on the detection results of theaforementioned distance enables driving toward the direction in whichthe image blurring decreases to be made quickly.

Further, in the case of switching the driving conditions of the secondlens unit while driving in order to generate the aforementionedinformation, performing weighting based on the detection results of theaforementioned distance relating to the conditions to switch the drivingcondition enables the switching of the driving conditions of the secondlens unit to be made according to the detecting distance, and theaforementioned information can be generated quickly.

As described above, according to the present embodiment, at the time ofgenerating the aforementioned information, weighting that corresponds tothe detecting distance can be added to the drive control of the secondlens unit, whereby the occurrence of image blurring can be reduced, andquick and smooth information generation can be realized. As a result,the focus of the focus objects can be maintained in a sure manner(following the zooming by the first lens unit).

Further, at the time of generating the aforementioned information usinga focal point signal that indicates the focal point state of theaforementioned optical system obtained from the photoelectric conversionsignals of the optical image formed by the optical system including thefirst and second lens units (for example, the re-generating process), byusing the drive control of the second lens unit or appropriately settingthe condition for drive condition switching of the second lens unit forthe so-called zigzag operation, problems can be avoided wherein thefocal point signal is influenced not only by changes in distance butalso changes in the appearance of the focus objects, the second lensunit drives and image blurring becomes noticeable.

While the present invention has been described with reference to whatare presently considered to be the preferred embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments. On the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. The scope of the following claims is to beaccorded the broadest interpretation so as to encompass all suchmodifications and equivalent structures and functions.

1. A lens control device for controlling the driving of a second lensunit for correcting image movement in the event of movement of avariating first lens unit, said lens control device comprising: astorage unit for storing data indicating the position of said secondlens unit corresponding to the position of said first lens unit createdfor a predetermined focal distance; a control unit for generatinginformation to control the driving of said second lens unit based onsaid data, and for controlling the driving of said second lens unitbased on this information; and a distance detecting unit for detectingthe distance to the focus object; wherein said control unit restrictsthe range of said generated information based on the detection resultsfrom said distance detecting unit.
 2. A lens control device according toclaim 1, wherein said information is locus information indicating theposition of said second lens unit as compared to said first lens unit.3. A lens control device according to claim 1, wherein said control unitgenerates said information using a focal point signal indicating thefocal point state of said optical system that is obtained fromphotoelectric conversion signals of the optical image formed by theoptical system that includes said first and second lens units.
 4. A lenscontrol device for controlling the driving of a second lens unit forcorrecting image movement in the event of movement of a variating firstlens unit, said lens control device comprising: a storage unit forstoring data indicating the position of said second lens unitcorresponding to the position of said first lens unit created for apredetermined focal distance; a control unit for generating informationto control the driving of said second lens unit based on said data, andfor controlling the driving of said second lens unit based on thisinformation; and a distance detecting unit for detecting the distance tothe focus object; wherein said control unit generates said informationbased on the detection results of said distance detecting unit and saiddata, and using this information as a reference, performs re-generatingprocessing that generates new said information using a focal pointsignal indicating the focal point state of said optical system that isobtained from photoelectric conversion signals of the optical imageformed by an optical system including said first and second lens unit;and wherein said control unit restricts the range of said generatedinformation based on the detection results from said distance detectingunit.
 5. A lens control device according to claim 4, wherein saidcontrol unit changes the driving conditions of said second lens unit todriving conditions at the time of driving based on information of saidreference, so that said second lens unit moves toward the position shownas the most focused condition of said focal point signal within saidregeneration process; and wherein the drive range of said second lensunit of this regeneration process is controlled based on the detectionresults of said distance detecting unit.
 6. A lens control deviceaccording to claim 5, wherein said control unit changes said drivingconditions for the drive range of said second lens unit in saidregeneration process so as to be restricted based on the detectionresults of said distance detecting unit.
 7. Optical equipmentcomprising: an optical system that includes said first and second lensunits; and the lens control device according to claim
 1. 8. A lenscontrol method for controlling the driving of a second lens unit forcorrecting image movement in the event of movement of a variating firstlens unit, said method comprising: a storage step for storing dataindicating the position of said second lens unit corresponding to theposition of said first lens unit created for a predetermined focaldistance; a control step for generating information to control thedriving of said second lens unit based on said data, and for controllingthe driving of said second lens unit based on this information; and adistance detecting step for detecting the distance to the focus object;wherein, in said control step, the range of said generated informationis restricted based on the detection results from said distancedetecting unit.
 9. A lens control method for controlling the driving ofa second lens unit for correcting image movement in the event ofmovement of a variating first lens unit, said method comprising: astorage step for storing data indicating the position of said secondlens unit corresponding to the position of said first lens unit createdfor a predetermined focal distance; a control step for generatinginformation to control the driving of said second lens unit based onsaid data, and for controlling the driving of said second lens unitbased on this information; and a distance detecting step for detectingthe distance to the focus object; wherein, in said control step, saidinformation is generated based on the detection results of said distancedetecting unit and said data, and using this information as a reference,re-generating processing is performed that generates new saidinformation using a focal point signal indicating the focal point stateof said optical system that is obtained from photoelectric conversionsignals of the optical image formed by an optical system including saidfirst and second lens unit; and wherein in said control step, the rangeof said generated information based on the detection results from saiddistance detecting unit is restricted.